Auxiliary device for power transmission line parameter test and test method

Abstract

The invention relates to the technical field of power systems, and discloses an auxiliary device for power transmission line parameter testing and a testing method.The auxiliary device comprises an A-phase knife switch, a B-phase knife switch, a C-phase knife switch, a grounding socket, an A-phase jack, a B-phase jack and a C-phase jack which are integrated on a rack; when the circuit is tested, the downlead of each phase is hung to the tail end of the corresponding tested circuit, the other end of the downlead of each phase is connected to the corresponding jack, and the grounding jack is connected with a grounding wire, so that when the circuit is tested, only the on-off state of the knife switch of each phase needs to be switched, and the grounding wire can be switched to the grounding jack. The grounding state of the tail end of a tested line of each phase can be conveniently and quickly adjusted by adjusting the grounding state of the tail end of the tested line of each phase, and a worker does not need to frequently and repeatedly perform high hanging and dismounting work on a down lead of each phase, so that manpower is greatly saved, meanwhile, the waiting time for dismounting the high hanging of the down lead is saved, the time for testing parameters of a power transmission line is greatly shortened, and the working efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and particularly to an auxiliary device and a testing method for testing transmission line parameters. Background Art

[0002] Line parameter measurement refers to using professional instruments to test the power line after cutover, obtaining a series of characteristic parameters such as the insulation, impedance, and capacitive reactance of the line, providing a scientific basis for daily operation and maintenance. During the line parameter measurement process, it is necessary to repeatedly change the grounding state of each phase of the line and test the parameters of each phase. When carrying out line relocation work, planned power outages will occur, so the time required for parameter measurement is closely related to the power outage time.

[0003] In the existing technology, line parameter measurement work includes preparatory work, safety measure arrangement, work permit, parameter testing, work termination, and wire removal and site cleaning. Among them, due to the time-consuming of the five links of preparatory work, safety measure arrangement, work permit, work termination, and wire removal and site cleaning being carried out according to the standardized operation execution card issued by the provincial company, it is impossible to compress the time for them. In the parameter testing link, the opposite side of the line needs to frequently switch the grounding state of each phase of the line according to the testing requirements of the main side, constantly remove the test rod and then connect it to different lines, which is time-consuming and laborious. The main side can only wait for the opposite side to complete the adjustment during this process, which is very time-consuming. Therefore, it is urgent to develop a new type of auxiliary device for line parameter measurement and a line switching method for the line switching step in the parameter testing link to shorten the time required for this link. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to shorten the parameter testing time. To solve the above technical problem, the present invention provides an auxiliary device for testing transmission line parameters, including a phase A knife switch, a phase B knife switch, and a phase C knife switch integrally arranged on a frame. One end of each of the phase A knife switch, the phase B knife switch, and the phase C knife switch is connected with a grounding socket, and the other sides of the phase A knife switch, the phase B knife switch, and the phase C knife switch are correspondingly connected with a phase A socket, a phase B socket, and a phase C socket. The phase A socket, the phase B socket, and the phase C socket are correspondingly connected with a phase A downlead, a phase B downlead, and a phase C downlead; the phase A socket, the phase B socket, and the phase C socket are also correspondingly connected with indicator lights.

[0005] Preferably, the frame is also integrally provided with a plurality of voltmeters, and the plurality of voltmeters are respectively used to monitor the voltages during the testing of the phase A line, the phase B line, and the phase C line.

[0006] The present invention also provides a method for testing transmission line parameters, including the following testing steps:

[0007] S1. Confirm the test site, and hang the A-phase downlead, B-phase downlead, and C-phase downlead high to the end of the corresponding line under test; then set up a fence and warning signs at the test site, place auxiliary devices, and connect the power supply and test equipment at the beginning of the line under test.

[0008] S2. Connect the bottoms of the A-phase downlead, B-phase downlead, and C-phase downlead to the A-phase jack, B-phase jack, and C-phase jack respectively, and then conduct the preliminary test for the transmission line parameter test.

[0009] S3. Conduct the DC resistance measurement. Close the A-phase knife switch, B-phase knife switch, and C-phase knife switch and confirm through the corresponding indicator lights, short-circuit the three phases at the end of the line under test, and open the circuit at the beginning of the line under test; the test equipment applies DC voltage between the A-phase line and the B-phase line, the B-phase line and the C-phase line, and the C-phase line and the A-phase line in turn, and obtains the DC voltage and DC current between the two phases, so as to obtain the DC resistance of each phase line; after the test is completed, open the A-phase knife switch, B-phase knife switch, and C-phase knife switch.

[0010] S4. Conduct the three-phase positive-sequence impedance test. Close the A-phase knife switch, B-phase knife switch, and C-phase knife switch and confirm through the corresponding indicator lights. At the same time, connect the grounding wire at the grounding socket to short-circuit and ground the end of the line under test; then apply a three-phase positive-sequence power supply with a frequency of f at the beginning, and then the test equipment measures and obtains the positive-sequence impedance of the line under test at this frequency; after the test is completed, open the A-phase knife switch, B-phase knife switch, and C-phase knife switch.

[0011] S5. Conduct the three-phase zero-sequence impedance test. Close the A-phase knife switch, B-phase knife switch, and C-phase knife switch and confirm through the indicator lights to short-circuit and ground the end of the line under test; connect the beginning of the line under test in parallel and connect the grounding device, apply a single-phase power supply with a frequency of f between the beginning and the grounding device, and then the test equipment measures and obtains the zero-sequence impedance of the line under test at this frequency; after the test is completed, open the A-phase knife switch, B-phase knife switch, and C-phase knife switch.

[0012] S6. Conduct the three-phase positive-sequence capacitance test. Confirm through the corresponding indicator lights that the A-phase knife switch, B-phase knife switch, and C-phase knife switch are in the open state, and make the end of the line under test in the open state; at the beginning of the line under test, the variable-frequency power supply three-phase isolation transformer applies a three-phase symmetric voltage to the three phases of the line under test through the test equipment, and the test equipment measures and obtains the positive-sequence capacitance of the line under test under power frequency; after the test is completed, zero the test power supply and open the A-phase knife switch, B-phase knife switch, and C-phase knife switch.

[0013] S7. Conduct a three-phase zero-sequence capacitance test. Confirm that the A-phase knife switch, B-phase knife switch, and C-phase knife switch are in the open state through the corresponding indicator lights, and make the end of the measured line in an open state. Short-circuit the head end of the measured line. The variable-frequency power supply single-phase isolation transformer applies a single-phase voltage to the measured circuit through the test equipment. The test equipment measures and obtains the voltage and current applied to the measured line, and then obtains the zero-sequence capacitance of the measured line under power frequency.

[0014] S8. Correctly record the test data, remove the test wiring, and restore the downlead.

[0015] Preferably, the preliminary test in step S2 includes the following steps:

[0016] S21. Induced voltage test under short-circuit state. Close the A-phase knife switch, B-phase knife switch, and C-phase knife switch, confirm the state through the corresponding indicator lights, and connect the grounding wire at the grounding socket. At the same time, the head end of the measured line is in an open state. Measure the induced voltage to the ground of each phase of A, B, and C at the head end through a capacitive voltage divider in turn.

[0017] S22. Induced voltage test under open-circuit state. Pull up the A-phase knife switch, B-phase knife switch, and C-phase knife switch to make both the head end and the end of the measured line in an open state. Measure the induced voltage at the end of each phase of A, B, and C in the open state at the head end through a capacitive voltage divider in turn.

[0018] S23. Induced current test. Close the A-phase knife switch, B-phase knife switch, and C-phase knife switch to make the end of the measured line in a short-circuit grounding state, and the head end of the measured line is also in a grounded state. Use a clamp-on ammeter to measure the grounding current of each phase at the head end of the line respectively. After the test, pull up the A-phase knife switch, B-phase knife switch, and C-phase knife switch.

[0019] S24. Phase check and line insulation resistance test. Close the B-phase knife switch and C-phase knife switch and open the A-phase knife switch to make the head end and end of the B-phase line and C-phase line in a short-circuit grounding state, and the head end and end of the A-phase line are suspended in an open state. Measure the insulation resistance of the A-phase line at the head end of the A-phase line with a megohmmeter, and preliminarily judge whether the phase identification at both ends of the A-phase line is consistent according to the insulation resistance value.

[0020] S25. Phase recheck. Pull down the A-phase knife switch to ground the end of the A-phase line, and measure the insulation resistance value of the A-phase line with a megohmmeter again, and judge whether the phases at both ends of the A-phase line are consistent through the insulation resistance value.

[0021] S26. Replace the A-phase line to be tested in step S24 and step S25 with the B-phase line and C-phase line in turn, and repeat the operations in step S24 and step S25 respectively to complete the insulation resistance measurement and phase check and phase recheck of the B-phase line and C-phase line.

[0022] Preferably, step S3 further includes step S31: recording the temperatures at both ends and along the line of the measured line during the process of obtaining the DC resistances of each phase line, and then converting the measured DC resistances of each phase line into the DC resistances at 20°C according to the temperatures during the measurement process.

[0023] Preferably, in step S4, the three-phase positive-sequence power supply adopts the output frequency points of 40Hz / 60Hz, the output voltage range is set to the low gear output of 250V, and a three-phase symmetrical voltage is applied to the measured line through the current input terminal - current output terminal of the test equipment from the 250V output L terminal of the three frequency conversion power supply isolation transformers. At the same time, the initial voltages to be measured are respectively connected to Ua, Ub, and Uc of the instrument, and the N terminal of the output of the frequency conversion power supply isolation transformer is connected to the Un terminal of the test equipment and reliably grounded.

[0024] Preferably, in step S5, the single-phase power supply adopts the output frequency points of 40Hz / 60Hz of the frequency conversion power supply, the output voltage range is set to the low gear output of 250V, and a single-phase voltage is applied to the short-circuited three-phase measured line through the A-phase current input terminal - A-phase current output terminal of the test equipment from the low gear output L terminal of a single frequency conversion power supply isolation transformer. The N terminal of the output of the frequency conversion power supply isolation transformer is connected to the Un terminal of the test equipment and reliably grounded.

[0025] Preferably, in step S6, the three-phase isolation transformer of the frequency conversion power supply adopts an output frequency of 60Hz, the output voltage range of the power supply is set to the high gear output of 750V, and a three-phase symmetrical voltage is applied to the three phases of the measured line through the current input terminal - current output terminal of the test equipment from the 750V output L terminal of the three-phase isolation transformer of the frequency conversion power supply. The N terminal of the output of the three-phase isolation transformer of the frequency conversion power supply is connected to the Un terminal of the test equipment and reliably grounded.

[0026] Preferably, in step S7, the single-phase isolation transformer of the frequency conversion power supply adopts an output frequency of 60Hz, the output voltage range of the power supply is set to the high gear output of 750V, and a single-phase voltage is applied to the measured line through the A-phase current input terminal - A-phase current output terminal of the test host from the 750V output L terminal of the single-phase isolation transformer of the frequency conversion power supply. The N terminal of the output of the frequency conversion power supply is connected to the Un terminal of the test host and ensured to be well grounded.

[0027] Preferably, after step S7, an insulation resistance test after the test is carried out. Close the knife switches of phase B and phase C and open the knife switch of phase A, so that the heads and tails of the phase B line and the phase C line are short-circuited and grounded, and the head and tail of phase A are suspended and in an open state; use a megohmmeter to measure the insulation resistance of the phase A line at the head of the phase A line.

[0028] Then, open the B-phase knife switch, close the A-phase knife switch and the C-phase knife switch, short-circuit and ground the heads and tails of the A-phase line and the C-phase line, leave the head and tail of the B-phase open and suspended, and use a megohmmeter to measure the insulation resistance of the B-phase line at the head of the B-phase line;

[0029] Finally, open the C-phase knife switch, close the A-phase knife switch and the B-phase knife switch, short-circuit and ground the heads and tails of the A-phase line and the B-phase line, leave the head and tail of the C-phase open and suspended, and use a megohmmeter to measure the insulation resistance of the C-phase line at the head of the C-phase line.

[0030] In the embodiment of the present invention, an auxiliary device and a test method for testing transmission line parameters have the following beneficial effects compared with the prior art:

[0031] In the present invention, an A-phase knife switch, a B-phase knife switch, and a C-phase knife switch are integrally provided on the frame, as well as an A-phase jack, a B-phase jack, and a C-phase jack corresponding to each phase of the knife switch. Before testing the line, first hang the down-lead wires of each phase high to the end of the respective line to be tested, and the other ends of the down-lead wires of each phase are connected to their respective corresponding jacks, while the grounding socket is connected to the grounding wire. When testing the line, only by switching the opening and closing states of each phase of the knife switch, the grounding state of the end of each phase of the line to be tested can be adjusted conveniently and quickly. The staff no longer needs to frequently hang and remove the down-lead wires of each phase, which greatly saves manpower. At the same time, the waiting time for removing and hanging the down-lead wires is eliminated, greatly reducing the time for testing the transmission line parameters and improving work efficiency. Description of the Drawings

[0032] Figure 1 is a schematic structural diagram of the auxiliary device of the present invention;

[0033] Figure 2 is a schematic test flow diagram of the present invention;

[0034] Figure 3 is of the present invention Figure 2 schematic flow diagram of the line parameter test;

[0035] Figure 4 is a schematic connection diagram of the steps for testing the induced voltage in the short-circuit state of the present invention;

[0036] Figure 5 is a schematic connection diagram of the steps for testing the induced voltage in the open-circuit state of the present invention;

[0037] Figure 6 is a schematic connection diagram of the steps for testing the induced current of the present invention;

[0038] Figure 7 is a schematic connection diagram of the steps for phase verification and line insulation resistance test of the present invention;

[0039] Figure 8 It is a schematic connection diagram in the phase review step of the present invention;

[0040] Figure 9 It is a schematic connection diagram in the DC resistance test step of the present invention;

[0041] Figure 10 It is a schematic connection diagram in the three-phase positive-sequence impedance test step of the present invention;

[0042] Figure 11 It is a schematic connection diagram in the three-phase zero-sequence impedance test step of the present invention;

[0043] Figure 12 It is a schematic connection diagram in the three-phase positive-sequence capacitance test step of the present invention;

[0044] Figure 13 It is a schematic connection diagram in the three-phase zero-sequence capacitance test step of the present invention.

[0045] In the figure: 1. Frame; 2. Phase A switch; 3. Phase B switch; 4. Phase C switch; 5. Grounding socket; 6. Phase A jack; 7. Phase B jack; 8. Phase C jack; 9. Indicator light; 10. Voltmeter. Detailed implementation manners

[0046] The following combines the accompanying drawings and embodiments to further describe in detail the detailed implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0047] As Figure 1 shown, a preferred embodiment of the present invention provides an auxiliary device for testing transmission line parameters, which includes a Phase A switch 2, a Phase B switch 3, and a Phase C switch 4 integrally arranged on a frame 1. One ends of the Phase A switch 2, the Phase B switch 3, and the Phase C switch 4 are all connected with a grounding socket 5, and the other sides of the Phase A switch 2, the Phase B switch 3, and the Phase C switch 4 are correspondingly connected with a Phase A jack, a Phase B jack 7, and a Phase C jack 8. The Phase A jack, the Phase B jack 7, and the Phase C jack 8 are correspondingly connected with a Phase A lead wire, a Phase B lead wire, and a Phase C lead wire; the Phase A jack, the Phase B jack 7, and the Phase C jack 8 are also correspondingly connected with an indicator light 9.

[0048] Furthermore, the frame 1 is also integrally provided with a plurality of voltmeters 10, and the voltmeters 10 are respectively used to monitor the voltages during the tests of the Phase A line, the Phase B line, and the Phase C line.

[0049] Specifically, in the embodiment of the present invention, the auxiliary device is arranged at the end of the circuit under test, corresponding to the test equipment at the head end of the circuit under test. When testing, it is necessary to adjust the state of the end of the circuit under test according to the state of the test equipment at the head end. An A-phase knife switch 2, a B-phase knife switch 3, a C-phase knife switch 4, an A-phase socket, a B-phase socket 7, a C-phase socket 8 and a grounding socket 5 are integrally arranged on the rack 1. When measuring the circuit under test, first hang the down-leads of each phase of the circuit under test high to the end of the corresponding circuit under test, and then insert the ends of the down-leads of each phase of the circuit under test into the A-phase socket, the B-phase socket 7 and the C-phase socket 8 respectively, and insert a grounding wire into the grounding socket 5. When the end of the circuit under test needs to cooperate with the test equipment at the head end for testing, the state of the end of each phase of the circuit in the circuit under test can be adjusted by opening and closing the A-phase knife switch 2, the B-phase knife switch 3 and the C-phase knife switch 4. The state of the end of each phase of the circuit in the circuit under test can be an open state, a grounded state, a three-phase short-circuit state, a two-phase short-circuit state, etc., which can meet the test requirements of the test equipment at the head end. There is no need to frequently remove and hang the down-leads of the circuit under test as in the prior art. When the test item changes, there is no need to wait for the switching of the down-leads, but directly switch different knife switches, so the test efficiency is higher and it is more convenient and fast.

[0050] In addition, in this embodiment, a voltmeter 10 is also provided corresponding to each phase socket. The staff at the end of the circuit under test can obtain the voltage values of each phase of the circuit under test through the voltmeter 10. The staff at the end of the circuit under test can better control the test state and progress of the transmission line parameters, and the communication between the staff at the end and the staff operating the test equipment at the head end is smoother, which can further improve the work efficiency.

[0051] Furthermore, a grounding knife switch can be set. The grounding knife switch is used to control the connection relationship between the grounding socket 5 and the A-phase knife switch 2, the B-phase knife switch 3 and the C-phase knife switch 4, so as to conveniently control the grounding state of each phase of the circuit under test, which is more convenient to use and has higher efficiency.

[0052] As Figures 2 to 3 shown, the present invention also provides a method for testing transmission line parameters, including the following test steps:

[0053] S1. Confirm the test site, and hang the A-phase down-lead, B-phase down-lead and C-phase down-lead high to the end of the corresponding circuit under test; then set up a fence and a warning sign at the test site, place the auxiliary device and connect the power supply and test equipment at the head end of the circuit under test.

[0054] S2. Connect the bottoms of the A-phase down-lead, B-phase down-lead and C-phase down-lead to the A-phase socket, B-phase socket 7 and C-phase socket 8 respectively, and then conduct the preliminary test of the transmission line parameter test.

[0055] S3. Conduct DC resistance measurement. Close the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 and confirm through the corresponding indicator lights 9. Short-circuit the three phases at the end of the line to be measured and open the head end of the line to be measured. The testing equipment sequentially applies DC voltage between the A-phase line and the B-phase line, between the B-phase line and the C-phase line, and between the C-phase line and the A-phase line, and obtains the DC voltage and DC current between the two phases, and then obtains the DC resistance of each phase line. After the test is completed, open the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4.

[0056] S4. Conduct three-phase positive-sequence impedance test. Close the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 and confirm through the corresponding indicator lights 9. At the same time, connect the grounding wire at the grounding socket 5 to short-circuit and ground the end of the line to be measured. Then apply a three-phase positive-sequence power supply with a frequency of f at the head end. Subsequently, the testing equipment measures and obtains the positive-sequence impedance of the line to be measured at this frequency. After the test is completed, open the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4.

[0057] S5. Conduct three-phase zero-sequence impedance test. Close the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 and confirm through the indicator light 9 to short-circuit and ground the end of the line to be measured. The head end of the line to be measured is shunted and connected to the grounding device in parallel. Apply a single-phase power supply with a frequency of f between the head end and the grounding device. Subsequently, the testing equipment measures and obtains the zero-sequence impedance of the line to be measured at this frequency. After the test is completed, open the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4.

[0058] S6. Conduct three-phase positive-sequence capacitance test. Confirm through the corresponding indicator lights 9 that the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 are in the open state, and make the end of the line to be measured in an open state. At the head end of the line to be measured, the variable-frequency power supply three-phase isolation transformer applies a three-phase symmetrical voltage to the three phases of the line to be measured through the testing equipment. The testing equipment measures and obtains the positive-sequence capacitance of the line to be measured under power frequency. After the test is completed, zero the test power supply and open the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4.

[0059] S7. Conduct three-phase zero-sequence capacitance test. Confirm through the corresponding indicator lights 9 that the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 are in the open state, and make the end of the line to be measured in an open state. The head end of the line to be measured is short-circuited. The variable-frequency power supply single-phase isolation transformer applies a single-phase voltage to the measured circuit through the testing equipment. The testing equipment measures and obtains the voltage and current applied to the measured lower circuit, and then obtains the zero-sequence capacitance of the line to be measured under power frequency.

[0060] S8. Correctly record the test data, remove the test wiring, and restore the downlead.

[0061] Specifically, when performing parameter tests on the circuit under test, preparation work such as clearing the site shall be done in advance according to the operation specifications. Then, the test equipment and auxiliary devices shall be prepared at the head end and the tail end of the circuit under test respectively. After connecting the test equipment at the head end of the circuit under test to the circuit under test, the down-leads of each phase shall be hung high to the corresponding phase lines at the tail end of the circuit under test. Then, the bottom ends of the down-leads of each phase shall be correspondingly connected to the jacks of each phase on the auxiliary device, and the grounding wire shall be connected to the grounding socket 5 of the auxiliary device to complete the connection work of the auxiliary device at the tail end of the circuit under test, so as to facilitate the normal progress of the subsequent circuit parameter test work. When the connection of the auxiliary device is completed and the preliminary tests are done, the test work of the transmission line parameters can be formally carried out, and the tests of the DC resistance, positive sequence impedance, zero sequence impedance, positive sequence capacitance and zero sequence capacitance shall be carried out in sequence according to the test requirements.

[0062] As Figure 9 shown, during the measurement of the DC resistance, the switch blades 2 of phase A, 3 of phase B and 4 of phase C are all closed, and the head end of the circuit under test is in an open state. Then, a DC voltage is applied between the phase A line and the phase B line through the test equipment to measure the DC voltage U AB and the DC current I AB . The total DC resistance R AB of the phase A and phase B lines is:

[0063] R AB =U AB / I AB

[0064] The inter-phase resistance R BC between the phase B and phase C lines and the inter-phase resistance R CA between the phase C and phase A lines are measured successively. Then, the DC resistance of each phase is:

[0065] R A =(R AB +R CA -R BC ) / 2

[0066] R B =(R AB +R BC -R CA ) / 2

[0067] R C =(R CA +R BC -R AB ) / 2

[0068] In the formula: R A is the DC resistance value of phase A; R B is the DC resistance value of phase B; R C is the DC resistance value of phase C.

[0069] As Figure 10 shown, during the three-phase positive-sequence impedance test, the measuring device extracts the three-phase voltage phasors of this frequency through signal analysis wherein the three-phase current phasors are and the positive-sequence short-circuit impedance Z S1 is:

[0070]

[0071] where: a = e j2π / 3 .

[0072] As Figure 11 shown, during the three-phase zero-sequence impedance test, the measuring device extracts the voltage phasor of this frequency through signal analysis current phasor and the zero-sequence short-circuit impedance Z S0 is:

[0073]

[0074] Among them, the three-phase positive-sequence capacitance test and the three-phase zero-sequence capacitance test can be obtained by calculating the vibration of the measuring instrument in the existing technology, so they will not be elaborated here; in some embodiments, the measuring device can also directly calculate parameters such as the DC resistance, positive-sequence impedance, and zero-sequence impedance of the measured line according to the above formula principle.

[0075] As Figures 4 to 8 shown, in some embodiments, the preliminary test in step S2 includes the following steps:

[0076] S21. Induced voltage test under short-circuit state: Close the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4, confirm the status through the corresponding indicator lights 9, connect the grounding wire at the grounding socket 5, and at the same time, the head end of the measured line is in an open state; measure the induced voltages to the ground of the A-phase line, B-phase line, and C-phase line at the head end through a capacitive voltage divider in turn;

[0077] S22. Induced voltage test under open-circuit state: Pull up the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 to make both the head end and the tail end of the measured line in an open state, and measure the induced voltages at the tail ends of the A-phase, B-phase, and C-phase in the open state at the head end through a capacitive voltage divider in turn;

[0078] S23. Induced current test: Close the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4 to make the tail end of the measured line in a short-circuit grounding state, and the head end of the measured line is also in a grounded state. Use a clamp-on ammeter to measure the grounding current of each phase at the head end of the line respectively. After the test, pull up the A-phase knife switch 2, B-phase knife switch 3, and C-phase knife switch 4;

[0079] S24. Phase verification and line insulation resistance test. Close the B-phase knife switch 3 and the C-phase knife switch 4 and open the A-phase knife switch 2, so that the heads and tails of the B-phase line and the C-phase line are short-circuited to the ground, and the head and tail of the A-phase are left open; use a megohmmeter to measure the insulation resistance of the A-phase line at the head of the A-phase line, and preliminarily judge whether the phase identification at both ends of the A-phase line is consistent according to the insulation resistance value;

[0080] S25. Phase re-verification. Open the A-phase knife switch 2 to ground the tail of the A-phase line, and measure the insulation resistance value of the A-phase line again with a megohmmeter, and judge whether the phases at both ends of the A-phase line are consistent through the insulation resistance value;

[0081] S26. Sequentially replace the A-phase line to be tested in step S24 and step S25 with the B-phase line and the C-phase line, and repeat the operations in step S24 and step S25 respectively to complete the insulation resistance measurement and phase verification and phase re-verification of the B-phase line and the C-phase line.

[0082] Among them, during the process of phase verification and line insulation resistance test on the line to be measured, measure the insulation impedance of the line to be measured corresponding to the phase. When the insulation impedance is not zero, it can be preliminarily judged that the phase identification at both ends of the line to be measured is consistent. For the re-verification of the phase, ground the tail of the phase line to be measured and measure the insulation resistance again. When the insulation resistance is zero, it can be judged that the phase identification at both ends of the line to be measured is consistent.

[0083] In some embodiments, step S3 further includes step S31: Record the temperature at both ends and along the line of the line to be measured during the process of obtaining the DC resistance of each phase line, and then convert the measured DC resistance of each phase line to the DC resistance at 20°C according to the temperature during the measurement.

[0084] Specifically:

[0085]

[0086] In the formula:

[0087] t—the average temperature along the line, unit: °C;

[0088] β—the resistance temperature rise coefficient of the line under test, unit: 1 / °C.

[0089] For ACSR, β = 0.0036 (1 / °C); for copper core cable, β = 0.00382 (1 / °C). R B,20℃ 、R C,20℃ The conversion method of the measurement result is the same as that of R A,20℃ .

[0090] Such asFigure 10 As shown, in some embodiments, in step S4, the three-phase positive-sequence power supply adopts output frequency points of 40Hz / 60Hz, the output voltage range is at the low-grade output of 250V, and a three-phase symmetrical voltage is applied to the line under test through the current input terminal - current output terminal of the test equipment from the 250V output L terminal of the three frequency conversion power supply isolation transformers. At the same time, the starting voltages to be measured are respectively connected to Ua, Ub, and Uc of the instrument, and the N terminal of the output of the frequency conversion power supply isolation transformer is connected to the Un terminal of the test equipment and reliably grounded. Among them, after the line is connected, the power supply is gradually adjusted from the zero position. When the applied test current reaches 6 - 8A, the three-phase phase voltages, three-phase currents, three single-phase active powers, and reactive powers applied to the line under test can be measured. The voltage is increased twice at 40Hz / 60Hz, and then the test equipment can respectively obtain the test data at the two frequency points of 40Hz and 60Hz. Subsequently, the test equipment can calculate and obtain parameter values such as the positive-sequence impedance, positive-sequence resistance, positive-sequence reactance, positive-sequence inductance, and impedance angle of the line.

[0091] As Figure 11 shown, in some embodiments, in step S5, the single-phase power supply adopts the output frequency points of 40Hz / 60Hz of the frequency conversion power supply, the output voltage range is at the low-grade output of 250V, and a single-phase voltage is applied to the short-circuited three-phase line under test through the A-phase current input terminal - A-phase current output terminal of the test equipment from the low-grade output L terminal of a single frequency conversion power supply isolation transformer. The N terminal of the output of the frequency conversion power supply isolation transformer is connected to the Un terminal of the test equipment and reliably grounded. Among them, the power supply is gradually adjusted from the zero position. When the applied test current reaches 6 - 8A, the voltage, current, active power, and reactive power applied to the line under test can be measured. The voltage is increased twice at 40Hz / 60Hz so that the test equipment can obtain the test data at the two frequency points of 40Hz and 60Hz. Subsequently, the test equipment can calculate and obtain parameter values such as the zero-sequence impedance, zero-sequence resistance, zero-sequence reactance, zero-sequence inductance, and impedance angle of the line.

[0092] As Figure 12 , in some embodiments, in step S6, the three-phase isolation transformer of the frequency conversion power supply adopts an output frequency of 60Hz, the output voltage range of the power supply is at the high-grade output of 750V, and a three-phase symmetrical voltage is applied to the three phases of the line under test through the current input terminal - current output terminal of the test equipment from the 750V output L terminal of the three-phase isolation transformer of the frequency conversion power supply. The N terminal of the output of the three-phase isolation transformer of the frequency conversion power supply is connected to the Un terminal of the test equipment and reliably grounded. Among them, the power supply is gradually adjusted from the zero position. When the applied test voltage reaches about 750V, the three-phase voltages and three-phase currents applied to the line under test are measured, and the test equipment can automatically calculate the positive-sequence capacitance and susceptance parameters of the line under power frequency.

[0093] As Figure 13, in some embodiments, in step S7, the single-phase isolation transformer of the variable-frequency power supply adopts an output frequency of 60 Hz, the output voltage range of the power supply is at the high-grade output of 750 V, and the 750 V output L terminal of the single-phase isolation transformer of the variable-frequency power supply applies a single-phase voltage to the line under test through the A-phase current input terminal - A-phase current output terminal of the test host. The N terminal of the variable-frequency power supply output is connected to the Un terminal of the test host and is ensured to be well grounded. Among them, the power supply is gradually adjusted from the zero position. When the applied test voltage reaches about 750 V, the voltage and current applied to the line under test are measured, and the test equipment can automatically calculate the zero-sequence capacitance and susceptance parameters of the line under power frequency.

[0094] , in some embodiments, after step S7, an insulation resistance test is performed after the test. Close the B-phase knife switch 3 and the C-phase knife switch 4 and open the A-phase knife switch 2 to short-circuit and ground the heads and tails of the B-phase line and the C-phase line. The head and tail of the A-phase are suspended and in an open state; use a megohmmeter to measure the insulation resistance of the A-phase line at the head of the A-phase line;

[0095] Then open the B-phase knife switch 3, close the A-phase knife switch 2 and the C-phase knife switch 4 to short-circuit and ground the heads and tails of the A-phase line and the C-phase line. The head and tail of the B-phase are suspended and in an open state. Use a megohmmeter to measure the insulation resistance of the B-phase line at the head of the B-phase line;

[0096] Finally, open the C-phase knife switch 4, close the A-phase knife switch 2 and the B-phase knife switch 3 to short-circuit and ground the heads and tails of the A-phase line and the B-phase line. The head and tail of the C-phase are suspended and in an open state. Use a megohmmeter to measure the insulation resistance of the C-phase line at the head of the C-phase line.

[0097] In summary, the embodiment of the present invention provides an auxiliary device and a test method for testing transmission line parameters. By setting the A-phase knife switch 2, the B-phase knife switch 3, and the C-phase knife switch 4, and the A-phase jack, the B-phase jack 7, and the C-phase jack 8 corresponding to each phase knife switch, it avoids the trouble of frequently removing and hanging the lead wire of the line under test high when performing different test items on the transmission line test. Just by cutting the knife switch corresponding to each phase line, the state of the line under test for each phase can be conveniently and quickly switched, making the test of transmission line parameters more convenient and fast, with higher efficiency and shorter test time.

[0098] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. An auxiliary device for testing transmission line parameters, characterized in that: It includes an A-phase switch, a B-phase switch and a C-phase switch integrated on a frame, wherein one end of the A-phase switch, the B-phase switch and the C-phase switch are connected to a grounding socket, and the other sides of the A-phase switch, the B-phase switch and the C-phase switch are correspondingly connected to an A-phase socket, a B-phase socket and a C-phase socket, and the A-phase socket, the B-phase socket and the C-phase socket are correspondingly connected to an A-phase down lead, a B-phase down lead and a C-phase down lead; the A-phase socket, the B-phase socket and the C-phase socket are also correspondingly connected to indicator lights.

2. The auxiliary device for testing transmission line parameters according to claim 1, characterized in that: The rack is also integrated with a plurality of voltmeters, which are respectively used to monitor the voltages of the A-phase line, the B-phase line and the C-phase line during testing.

3. A method for testing transmission line parameters, using the auxiliary device as claimed in any one of claims 1 to 2, characterized in that: The test steps include: S1. Confirm the test site, hang the A-phase down conductor, B-phase down conductor and C-phase down conductor to the end of the corresponding line under test; then set up fences and warning signs at the test site, place auxiliary devices and connect the power supply and test equipment at the head end of the line under test; S2. Connect the bottom ends of the A-phase down conductor, the B-phase down conductor and the C-phase down conductor to the A-phase socket, the B-phase socket and the C-phase socket respectively, and then conduct a preliminary test of the transmission line parameter test; S3, perform DC resistance measurement, close the A-phase switch, the B-phase switch and the C-phase switch and confirm through the corresponding indicator light, so that the three phases at the end of the measured line are short-circuited and the head end of the measured line is open; the test equipment applies DC voltage between the A-phase line and the B-phase line, the B-phase line and the C-phase line, and the C-phase line and the A-phase line in sequence, and obtains the DC voltage and DC current between the two phases, and then obtains the DC resistance of each phase line; after the test is completed, open the A-phase switch, the B-phase switch and the C-phase switch; S4, perform a three-phase positive sequence impedance test, close the A-phase switch, the B-phase switch and the C-phase switch and confirm through the corresponding indicator light, and connect the grounding wire at the grounding socket to short-circuit the end of the tested line to ground; then apply a three-phase positive sequence power supply with a frequency of f at the head end, and then the test equipment measures and obtains the positive sequence impedance of the tested line at this frequency; after the test, open the A-phase switch, the B-phase switch and the C-phase switch; S5. Perform a three-phase zero-sequence impedance test. Close the A-phase switch, the B-phase switch and the C-phase switch and confirm through the indicator light to short-circuit the end of the tested line to ground. Short-circuit the head end of the tested line in parallel and connect the grounding device. Apply a single-phase power supply with a frequency of f between the head end and the grounding device. Then the test equipment measures and obtains the zero-sequence impedance of the tested line at the frequency. After the test, open the A-phase switch, the B-phase switch and the C-phase switch. S6. Perform a three-phase positive-sequence capacitance test, confirm that the A-phase switch, B-phase switch and C-phase switch are in the open state through the corresponding indicator lights, so that the end of the tested line is in an open circuit state; at the head end of the tested line, the three-phase isolation transformer of the variable frequency power supply applies a three-phase symmetrical voltage to the three phases of the tested line through the test equipment, and the test equipment measures and obtains the positive-sequence capacitance of the tested line at the power frequency; after the test, adjust the test power supply to zero, and open the A-phase switch, B-phase switch and C-phase switch; S7, perform a three-phase zero-sequence capacitance test, confirm through the corresponding indicator lights that the A-phase switch, the B-phase switch and the C-phase switch are in the open state, so that the end of the tested line is in an open circuit state; the head end of the tested line is short-circuited, and the variable frequency power supply single-phase isolation transformer applies a single-phase voltage to the tested circuit through the test equipment, and the test equipment measures and obtains the voltage and current applied to the tested line, and then obtains the zero-sequence capacitance of the tested line at the power frequency; S8. Record the test data correctly, remove the test wiring, and restore the down lead.

4. The transmission line parameter testing method according to claim 3, characterized in that: The preliminary test in step S2 includes the following steps: S21, induced voltage test under short circuit state, close the A phase switch, B phase switch and C phase switch, confirm the status through the corresponding indicator light, and connect the ground wire at the grounding socket, while the head end of the tested line is in an open circuit state; the head end measures the induced voltage of phase A, phase B and phase C to the ground in turn through the RC voltage divider; S22, induced voltage test in open circuit state, pull up the A phase switch, B phase switch and C phase switch, so that the head end and the end of the tested line are in open circuit state, and measure the induced voltage of A phase, B phase and C phase in the open circuit state in sequence at the head end through the RC voltage divider; S23, induction current test, close the A-phase switch, B-phase switch and C-phase switch, so that the end of the tested line is in a short-circuit grounding state, and the head end of the tested line is also in a grounding state, use a clamp ammeter to measure the grounding current of each phase at the head end of the line, and pull up the A-phase switch, B-phase switch and C-phase switch after the test; S24, phase check and line insulation resistance test, close the B-phase and C-phase switches and open the A-phase switch, so that the beginning and end of the B-phase and C-phase lines are short-circuited to ground, and the beginning and end of the A-phase are suspended in an open circuit state; use a megohmmeter at the beginning of the A-phase line to measure the insulation resistance of the A-phase line, and preliminarily determine whether the phase identification marks at both ends of the A-phase line are consistent based on the insulation resistance value; S25, phase check, pull down the A phase switch to ground the end of the A phase line, measure the insulation resistance value of the A phase line with the megohmmeter again, and judge whether the phase difference at both ends of the A phase line is consistent through the insulation resistance value; S26. Replace the A-phase circuit to be tested in step S24 and step S25 with the B-phase circuit and the C-phase circuit in sequence, and repeat the operations in step S24 and step S25 to complete the insulation resistance measurement of the B-phase circuit and the C-phase circuit as well as the phase verification and phase recheck.

5. The transmission line parameter testing method according to claim 3, characterized in that: Step S3 also includes step S31: recording the temperature at both ends and along the measured line in the process of obtaining the DC resistance of each phase line, and then converting the measured DC resistance of each phase line into a DC resistance at 20° C. according to the temperature during the measurement process.

6. The transmission line parameter testing method according to claim 3, characterized in that: In step S4, the three-phase positive sequence power supply adopts 40Hz / 60Hz output frequency point, and the output voltage is at 250V low-level output. The 250V output L end of the three frequency conversion power isolation transformers applies a three-phase symmetrical voltage to the measured circuit through the current input end and current output end of the test equipment. At the same time, the starting end voltage to be measured is respectively connected to Ua, Ub, and Uc of the instrument. The output N end of the frequency conversion power isolation transformer is connected to the Un end of the test equipment and is reliably grounded.

7. The transmission line parameter testing method according to claim 3, characterized in that: In step S5, the single-phase power supply adopts the 40Hz / 60Hz output frequency point of the variable frequency power supply, and the output voltage is set at a low-speed output of 250V. A single-phase voltage is applied to the short-circuited three-phase measured circuit from the low-speed output L end of a single variable frequency power supply isolation transformer through the A-phase current input end and the A-phase current output end of the test equipment. The N-end of the output of the variable frequency power supply isolation transformer is connected to the Un end of the test equipment and is reliably grounded.

8. The transmission line parameter testing method according to claim 3, characterized in that: In step S6, the three-phase isolation transformer of the variable frequency power supply adopts an output frequency of 60Hz, the output voltage gear of the power supply is set to 750V high-end output, the 750V output L end of the three-phase isolation transformer of the variable frequency power supply applies a three-phase symmetrical voltage to the three phases of the measured circuit through the current input end and current output end of the test equipment, and the output N end of the three-phase isolation transformer of the variable frequency power supply is connected to the Un end of the test equipment and is reliably grounded.

9. The transmission line parameter testing method according to claim 3, characterized in that: In step S7, the single-phase isolation transformer of the variable frequency power supply adopts an output frequency of 60Hz, the output voltage gear of the power supply is set to 750V high-end output, the 750V output L end of the single-phase isolation transformer of the variable frequency power supply applies a single-phase voltage to the measured circuit through the A-phase current input end and the A-phase current output end of the test host, and the N-end of the variable frequency power supply output is connected to the Un end of the test host and connected in parallel to ensure good grounding.

10. The transmission line parameter testing method according to claim 3, characterized in that: After step S7, a post-test insulation resistance test is performed, the B-phase switch and the C-phase switch are closed and the A-phase switch is opened, so that the beginning and the end of the B-phase line and the C-phase line are short-circuited to ground, and the beginning and the end of the A-phase line are suspended in an open circuit state; the insulation resistance of the A-phase line is measured at the beginning of the A-phase line using a megohmmeter; Then open the B-phase switch, close the A-phase switch and the C-phase switch, so that the beginning and the end of the A-phase line and the C-phase line are short-circuited to ground, and the beginning and the end of the B-phase line are suspended in an open circuit state. The insulation resistance of the B-phase line is measured with a megohmmeter at the beginning of the B-phase line. Finally, open the C phase switch and close the A phase switch and the B phase switch to short-circuit the beginning and end of the A phase line and the B phase line to ground. The beginning and end of the C phase are left suspended in an open circuit state. A megohmmeter is used at the beginning of the C phase line to measure the insulation resistance of the C phase line.

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